Limit switch



1954 J.-N. ANDERSON ETAL 2,670,415

LIMIT SWITCH Filed May 2, 1952 7 AT ORNEY Patented Feb. 23, :19 54 LIIWIT SWITCH James N. Anderson, Caldwell, and Wilton S. Viall, Jr., Millburn, N. J assignors to Curtiss-Wright Corporation, a corporation Application May 2, 1952, Serial No. 285,657

Claims. (01. 200-70) This invention relates to snap action electrical switches and is concerned, in particular, with a switch snap action incorporating latching arrangements.

While it is realized that the prior art teaches latching snap action switches, the switch of this invention is considered to be more simple and direct in its action than those of the prior art, and incorporates over-riding means by which action of the switch may be enforced by the operating member if, through failure of some of the switch parts, the elastic snap action fails to operate.

A typical arrangement of the switch of this invention is shown in the accompanying drawings which show the principles of operation. The embodiment shown in the drawin s. however, is not deemed to limit the scope of the invention since the switch action may be adapted to a multitude of purposes for enabling precise switch operation according to the position of the operating members. A switch of this sort may, for instance, be utilized for limit stops in machine tools, in electrically actuated aircraft propellers and other environments.

Referring to the drawings, Figs. 1, 2. and 3 are frontal elevations of the switch and its component parts shown in diflerent positions of adjustment,

"and Figs. 4 and 5 are sections on the lines 44 and 55 of Fig. 3.

The switch comprises a supporting structure or housing [0 which may conveniently be arranged as a closable box having a cover l2 whichmay be secured thereto as by screws. To one wall of the "support, a pivot I4 is securely attached and upon this pivot I4 an operating member I6 is journalled, to swing back and forth through an appropriate angle. The member l6, as shown, includes an operating handle l8 which may be replaced with some device which is appropriate for cooperating with cams or other actuating devices comprising parts of a mechanism. The member l6 includes a depending portion 26 which is bored to receive a spring 22 and a ball 24, the ball bear- .ing upon a platform 26 formed on the upper part of a rocker 28. The rocker is journalled on With the elements in the position 28 at a point Ofi-set from the pivot 30, thereby pressing the rocker 28 in a clockwise direction. -When the memberlfi is swung clockwise as shown in Fig.2., the ball travels along the platform 26 to the other side of a line joining the pivots I4 and 30, urging the rocker 28 in a counter-clockwise direction.

At the ends of the platform 26 raised ramps 32 are provided. If the member I6 is moved far enough, for instance clockwise as shown in Fig. 2, and if the rocker 28 fails to rock in counterclockwise direction under the influence of the spring 22, the lower end 20 of the member I6 will bear upon the left hand ramp 32 and force movement of the rocker 28 in a counter-clockwise direction.

In order to restrain rocking of the rocker 28 until a certain angular travel of the handle l8 has been effected, a pair of arms 34 and 36 are swung on the pivot l4. These arms are urged apart by a spring 38 which, as shown, embraces the pivot I4 and bears on the inner sides of the arms 34 and 36, urging them apart and into engagement with abutments 40 and 42 formed on the member l6.

On the rocker 2B and in the plane of the arms 34 and 36 we provide space for shoulders 44 and 46 which rise-from a recessed portion 46 formed in the rocker. These shoulders 44 and '46 provide stops to prevent rocking of the rocker 28 when engaged by one or'the other of the arms 34 and 36.

Referring to Fig. 1; it will be noted that rocker 28 is in its extreme clockwise position. When it is desired to throw the rocker in a counterclockwise direction the handle [6 is swung clockwise. As this clockwise movement occurs, the abutment 40 presses the arm 34 to the left. When the ball 24 is over-center, the rocker 23 is urged in a counter-clockwise direction by the ball 24 but is prevented from turning by the engagement of the arm 34 with the shoulder 44. As clockwise movement of the member I6 continues, the position of Fig. 2 is reached where the arm'34 drops off the shoulder 44, leaving the spring 22 and ball 24 free to snap the'rocker 28 in the counter-clockwise direction, whereupon the right hand end of the rocker 28 rises so that the arm 34 occupies tion.

When the handle I8 is moved to the left, a sequencesimilar to that above described takes place except in reverse. That is, the arm 36 bears on the shoulder 46 and is gradually moved to the right off the shoulder, as the handle l8 moves counter-clockwise. At a particular point in the movement of the handle 18, the arm 36 drops off the shoulder 46 permitting the rocker 48 to snap in a clockwise direction under the influence of the spring 22.

Thus, it will be seen that we have provided a snap action arrangement where the. snap of the rocker 28 in either direction is precisely controlled, in response to the direction of motion of the handle l8 and to precise positions of the handle 18 during its travel.

The switching accomplished. by; the. rocker 28- is attained by mounting a. pair of contacts: 50

and 52 at the bottom of the support l0. A bridge. piece 54 carrying contacts 56 is. mounted on the. rocker 28, which at times connects the contacts 50 and 52. The bridge piece is loosely mounted upon a pin 58 secured in the rocker 28, the bridge piece. being urged downwardly by a. spring 60. When the rocker 28 movesv to its counter-clockwise position the contacts 56 will engage the contacts 50 and 52 toclose-an, appropriateelectrical circuit. The spring 60, is desirable to assume tolerances allowed by slight, oscillation oi the rocker 28 during shift; or the loading, ball. 24. to either side of the center position defined, by the line between the pivots; I4. and 30. The head on the pin 58 afiords positive separation of thezcontacts. when the rocker. is. moved away fromthe fixed contacts.

A similar set of, contacts. to those shownin Fig. may be arranged onthe; other side of; the housing; it so that a circuit may be made or broken for either direction ofswing, of the switch. Alternatively. in a. manner which is. well known in the art, the switch points may be: rearranged to provide forthe. simultaneousmaking or breaking of two circuit lines for one throw of the switch. Various other switching; combinations may be arranged.

The arrangement shown susceptible to a variety ofrearrangements in; detailed structure. For instance, the spring 38; may comprise leaves or any other resilient device; toseparatethearms 3A; and. 36; andto; urge them. at. all times into. engagement with the abutments 40 and 42; respectively; The loading spring 22 is susceptible to various arrangements: to; provide the force necessary to urge the rocker; 28in. one. direction or the other, in. response to. movement; of. the. operatingmember- (6..

Preferably, the rocker; 28 is, provided with, hard surfaces on the tops; and: corners ofthe. shouliders M 46; and on the. platform 26, to minimize wear;

Though one embodiment of the; invention is shown it: is to be understood, that: theiinvention may be applied in various. forms andzin' various enviroments. Changes may Ice-made. in the arrangements shown; without; departing. from. the spirit of the invention. Reference: should:v be had to the appended claims; for: definition. of the limits of, the invention.

What is; claimed; is:

1'. A. snapswitch comprising; a. supygiort, anop erating. member pivoted: thereon-, said member including: a pair of; opposed abutments. spaced from. pivotand. including a spring: presser having,v a line, of action radial relative. to said pivot, the line of action lying substantially mid,- way between said. abutments. and. in a. plane spaced, therefrom, a. pair; of. elements mounted onsaidpivot and-extending, along. said member,

lying between said abutments and each engageable with one abutment, resilient means spreading said elements apart toward engagement with respective abutments, a rocker pivoted on said support having a track engaged by said spring presser, said rocker having spaced dogs engageable at times by said elements, an electrical contact carried by said rocker, and an: electrical contact on the support engageable by the rocker contact and disengageable therefrom as the rocker is swung on its pivot, said track having inclined ramps atits ends for engagement by said member for enforcing rocker movement upon failure of said spring presser to move the rocken.

2.. A map: switch comprising a support, an operating member pivoted thereto for limited swinging, a'rocker pivoted on the support for limited. swinging, said pivots being spaced from one another, resilient means acting between the member and rocker operable to swing the rocker counter-clockwise as the member is swung clockwise and vice versa, latching. means normally operative to hold the rocker against swinging movement, an abutment on the member for positively moving said latching means with the member as the latter is swung, a releaseshoulder on the rocker on which the latching means normally bears, said latching, means upon. member movement, moving. 011 said shoulder'to allow rocking of the rocker under the influence-of said resilient means, and. coactable electric contacts on the rocker and support, said rocker having ramps thereon engageable by the: operating member to enforce rocker movement upon failure of the resilient means to move the rocker.

3. A snap switch comprising; a pivoted switch rocker having a contact, a fixed contact engageable thereby; means for moving said rocker to engage and disengage said contacts including a separately pivoted operating member, resilient means between said memberand rocker for org:- ingmovement of said rocker upon movementv of said member; means for latching. said rocker in contact-engaged and. contact-disengaged positions, including spaced shoulder on. the rocker,

latch arms movable-with and: with respect to the operating member'and engageableat times with said shoulders, abutments on the operating member engageable with the latch arms;.and resilient. means urging the latch arms into engagement with said abutments and additional abutment means on the rocker contactable by the operating. member uponover-swing thereof toenforce-rocker movement after release of the rocker by a latch arm, should the: rocker have failed-.toswing'under the influence of said resilient means.

4. A latching snap switch comprising-a pivoted rocker havinga contact thereon; a; fixed contact engageablethereby, saidrockerbeing swingable through alimited' angle to engageanddisengage said; contacts, said: rocker having a platform with a. hard Wear-surface andtabutments: at" eachend of the. platform. said rocker: also having; in; a plane spaced from: the platform; plane,v a. depressed. portion: and shoulders at each endzof'th'e depressed portion; arr operating? member-pivoted on an .axisspaced. from and parallel tothe rocker pivot, said member including a: resilient; presser engaged with the rocker. platform and: movable therealong upon movement of the member to exert a: force on the rocker to swing it one way or the. other-depending on which side ofthe rocker. center. the. presser. bears, said member. be:-

ing engageable with one or the other of said rocker platform abutments to enforce rocker swinging; a pair of swingable latch arms on said member pivot, means to urge said arms apart, spaced abutments on the member, spaced from the member pivot, one disposed on the outside of each latch arm and engageable therewith, said latch arms extending to the zone of said rocker shoulders and. being engageable therewith to prevent swinging of said rocker, each said latch arm being movable at times by the member abutment to disengage the corresponding rocker shoulder, and to allow rocker swinging under the urging of said resilient presser.

5. A latching snap switch comprising a pivoted rocker having a contact thereon, a fixed contact engageable thereby, said rocker being swingable through a limited angle to engage and disengage said contacts, said rocker having a platform with a hard wear-surface and abutments at each end of the platform, said rocker also having, in a plane spaced from the platform plane, a depressed portion and shoulders at each end of the depressed portion; an operating member pivoted on an axis spaced from and parallel to the rocker pivot, said member including a resilient presser engaged with the rocker platform and movable therealong upon movement of the member to exert a force on the rocker to swing it one way or the other depending on which side of the rocker center the presser bears, said member being engageable with one or the other of said rocker platform abutments to enforce rocker swinging; a pair of swinging latch arms pivoted on the switch, each having a portion extending to the zone of said rocker shoulders and being engageable therewith to prevent swinging of said rocker, resilient means urging said latch arms into positions to interrupt movement of said rocker, and abutment means on said operating member engageable at times with one or the other of said latch arms, each said latch arm being moveable at times by the member abutment means to disengage said rocker and to allow movement of said rocker under the urging of said resilient presser.

JAMES N. ANDERSON. WILTON s. VIALL, JR.

References Cited in the file of this patent I UNITED STATES PATENTS Number Name Date 2,390,365 Goff Dec. 4, 1945 2,586,075 Miller Feb. 19, 1952 FOREIGN PATENTS Number Country Date 274,547 Germany May 28, 1914 

